MST and PNT have the potential to be used for all patients with mtDNA disorders, which may make them preferential to PGD in the future. In patients with homoplasmy or high levels of heteroplasmy, these are the only techniques that would make it possible for them to have a genetically related unaffected child.

4.3.6

There is currently insufficient evidence to recommend one transfer technique over the other.

4.3.7

Although potentially useful clinical techniques, further safety experiments need to be done before introducing them into clinical practice.

4.3.8

Once assessed as safe to use in clinical practice, the panel strongly recommends that permission is sought from the parents of the children born from MST and PNT to be followed up for an extensive period.

5.1

From the evidence received, the panel has not identified anything that indicates that the MST and PNT methods are unsafe. Nevertheless, these techniques are relatively novel, especially as applied to human embryos, and with relatively few data. The panel therefore recommends that additional studies be undertaken both on basic research to improve the knowledge about the biology of human mitochondria and on research aimed specifically at providing further safety information on MST and PNT.

5.2

Basic research is needed into how the mitochondrial bottleneck functions and the critical parameters involved in the segregation of normal and any specific abnormal mitochondria amongst cell types in humans, as this is generally not well understood. For example, in the long term it may eventually be possible to influence or control replication of abnormal mtDNA in the early embryo to affect its segregation or inheritance in